OBJECTIVES: To evaluate and compare bone tunnel positioning in anterior cruciate ligament (ACL) reconstruction surgery using the arthroscopic technique and the open technique consisting of arthrotomy. METHOD: A comparative retrospective study on 70 patients with ACL lesions was conducted. Thirty-five patients underwent ACL reconstruction by means of the open technique and 35 by means of the arthroscopic technique using an anteromedial portal. All the patients underwent ACL reconstruction using an autologous graft from the middle third of the patellar tendon, fixed using interference screws. The postoperative radiographs were reviewed and the positioning of the femoral tunnel was evaluated using the methods proposed by Harner and Aglietti, while the tibial tunnel was assessed using the method proposed by Rauschning and Staubli. RESULTS: Fifty-four of the patients were male and 16 were female. Their mean age at the time of the procedure was 34 years and 3 months, with a range from 17 to 58 years. The arthroscopic technique was shown to be more accurate than the open technique for positioning both the femoral and the tibial bone tunnels. CONCLUSIONS: Radiological analysis on the knees subjected to ACL reconstruction showed that the positioning of both the femoral and the tibial bone tunnels presented less variation when the surgery was performed arthroscopically.